PHP生成随机或者唯一字符串

/**
* [生成随机字符串]
* @E-mial wuliqiang_aa@163.com
* @TIME   2017-04-07
* @WEB    http://blog.iinu.com.cn * @param  integer $length [生成的长度]
* @param  integer $type   [生成的类型]
* @return [type]   str       [description]
* @php 随机码类型：0，数字+大写字母；1，数字；2，小写字母；3，大写字母；4，特殊字符；-1，数字+大小写字母+特殊字符
*/
function randCode($length = 5, $type = 0) {
$arr = array(1 => "0123456789", 2 => "abcdefghijklmnopqrstuvwxyz", 3 => "ABCDEFGHIJKLMNOPQRSTUVWXYZ", 4 => "~@#$%^&*(){}[]|");
if ($type == 0) {
array_pop($arr);
$string = implode("", $arr);
} else if ($type == "-1") {
$string = implode("", $arr);
} else {
$string = $arr[$type];
}
$count = strlen($string) - 1;
for ($i = 0; $i < $length; $i++) {
$str[$i] = $string[rand(0, $count)];
$code .= $str[$i];
}
return $code;
}

/**
* [生成唯一字符串]
* @E-mial wuliqiang_aa@163.com
* @TIME   2017-04-07
* @WEB    http://blog.iinu.com.cn * @ 0-存数字字符串；1-小写字母字符串；2-大写字母字符串；3-大小写数字字符串；4-字符；
*   5-数字，小写，大写，字符混合
* @param  integer $type   [字符串的类型]
* @param  integer $length [字符串的长度]
* @param  integer $time   [是否带时间1-带，0-不带]
* @return [string]  $str    [返回唯一字符串]
*/
function randSole($type = 0,$length = 18,$time=0){
$str = $time == 0 ? '':date('YmdHis',time());
switch ($type) {
case 0:
for((int)$i = 0;$i <= $length;$i++){
if(mb_strlen($str) == $length){
$str = $str;
}else{
$str .= rand(0,9);
}
}
break;
case 1:
for((int)$i = 0;$i <= $length;$i++){
if(mb_strlen($str) == $length){
$str = $str;
}else{
$rand = "qwertyuioplkjhgfdsazxcvbnm";
$str .= $rand{mt_rand(0,26)};
}
}
break;
case 2:
for((int)$i = 0;$i <= $length;$i++){
if(mb_strlen($str) == $length){
$str = $str;
}else{
$rand = "QWERTYUIOPLKJHGFDSAZXCVBNM";
$str .= $rand{mt_rand(0,26)};
}
}
break;
case 3:
for((int)$i = 0;$i <= $length;$i++){
if(mb_strlen($str) == $length){
$str = $str;
}else{
$rand = "123456789qwertyuioplkjhgfdsazxcvbnmQWERTYUIOPLKJHGFDSAZXCVBNM";
$str .= $rand{mt_rand(0,35)};
}
}
break;
case 4:
for((int)$i = 0;$i <= $length;$i++){
if(mb_strlen($str) == $length){
$str = $str;
}else{
$rand = "!@#$%^&*()_+=-~`";
$str .= $rand{mt_rand(0,17)};
}
}
break;
case 5:
for((int)$i = 0;$i <= $length;$i++){
if(mb_strlen($str) == $length){
$str = $str;
}else{
$rand = "123456789qwertyuioplkjhgfdsazxcvbnmQWERTYUIOPLKJHGFDSAZXCVBNM!@#$%^&*()_+=-~`";
$str .= $rand{mt_rand(0,52)};
}
}
break;
}
return $str;
}